According to a known driver monitoring system, an image of a face of the driver is taken and processed so as to be used for executing a driving assist control. In order to appropriately execute the driving assist control by means of the driver monitoring system, the image of the driver's face needs to be appropriately taken. However, with respect to an environment where the image of driver's face is taken, because an exposure condition may vary depending on weather, season, a traveling state and the like, the exposure condition may not be stably maintained easily. Further, because in-vehicle parts such as a sun visor and a pillar may make a sharp shadow on the driver's face, it may also be difficult to capture the image appropriately by means of a camera having sensitivity for a visible range.
According to JP2005-271876A, an imaging apparatus has been disclosed in which, in order to take the image appropriately, a driver's face is irradiated with near-infrared lights emitted from upper and lower by means of LED (Light Emitting Diode). In this configuration, the image of the driver's face is taken under a circumstance where no shadow or little shadow exists on the driver's face.
Further, according to JP 2005-301742A, a verification system has been disclosed in which, the image of the driver's face is taken for a personal verification. Specifically, the image of the driver's face is taken where a near-infrared LED irradiates the driver with a light, and a driving current for light emission supplied to the near-infrared LED is controlled in order to increase the life of the near-infrared LED.
According to JP2006-248363A, another imaging apparatus has been disclosed in which a near-infrared LED is provided in a rear visual field where the driver monitors the rear visual field through a rear view mirror. The near-infrared LED irradiates an inside of the rear view mirror direction with near-infrared rays. The near infrared rays are reflected by an inside of the rear view mirror and illuminates the face of the driver.
However, as the vehicle travels fast, the exposure condition to the external light (sunlight) varies every moment. Further, the exposure condition varies depending on weather and seasonal change. Thus, the apparatuses and systems disclosed in JP2005-271876A, JP2005-301742A and JP2006-248363A may not reduce influences due to the external light. Specifically, when the near-infrared LED is not appropriately positioned, the influence of the sunlight is not diminished. For example, when a shadow is made on the driver's face due to the sunlight or the like, the face image may not be taken appropriately. Further, when the face of the driver who is wearing a reflector such as eyeglasses is irradiated with a high-intensity light such as the sunlight, the high-intensity light reflects on the reflector, and the face image may not be taken appropriately. By means of an optical band-pass filter, a visible optical element in the reflected light that enters the camera may be filtered.
Further, in methods disclosed in JP2005-271876A, JP2005-301742A and JP2006-248363A, a reference for setting the number of the near-infrared LED is not provided. Accordingly, excessive near-infrared LEDs may be provided, as a result, a level of electric power consumption may be increased.
A need thus exists for an imaging apparatus and a lighting apparatus for imaging which is not susceptible to the drawback mentioned above.